In radio communications, the spatial division multiple access (SDMA) scheme using an adaptive array antenna is well known as a technique allowing effective use of frequency resources. The use of the adaptive array antenna enables communication with a communication destination located in a specific direction by adaptively forming a directional beam by the multiple antenna elements.
IEEE802.16e (Mobile WiMAX (trademark)) is known as a radio communication system employing the SDMA scheme. In the standard specification of IEEE802.16e, an AAS (Adaptive Array antenna System) diversity map is provided as an option in a downlink frame (hereinafter referred to as “DL frame”) (See Non-Patent Document 1 and Non-Patent Document 2).
FIG. 1 shows a configuration of a TDD (Time Division Duplex) frame, including the AAS diversity map option, described in Non-Patent Documents 1 and 2. A broadcast map is provided in a frame header of the DL frame.
A broadcast map is control information notified to mobile stations through a channel shared by multiple mobile stations, that is, through a broadcast channel. The broadcast map also includes a DL map that is allocation information of downlink data bursts, and an UL map that is allocation information of uplink data bursts. In contrast, an AAS diversity map is transmitted by using a beamforming transmission or a diversity transmission to a certain mobile station by an AAS function of the base station.
If, at a cell edge, the mobile station cannot acquire the broadcast map transmitted by the base station, the mobile station scans the AAS diversity map preceded by the broadcast map in the same frame.
The AAS diversity map includes allocation information of the broadcast map transmitted by the beamforming at other channels. The mobile station receives the broadcast map transmitted by the beamforming on the basis of the allocation information included in the AAS diversity map.
Non-Patent Document 1: IEEE Std 802.16e 2005
Non-Patent Document 2: IEEE Std 802.16-2004/Corl-2005